Synthesis of quaternary reversible/quantum comparators

Multiple-valued quantum circuits are promising choices for future quantum computing technology, since they have several advantages over binary quantum circuits. Quaternary logic has the advantage that classical binary functions can be very easily represented as quaternary functions by grouping two bits together into quaternary values. Grover’s quantum search algorithm requires a sub-circuit called oracle, which takes a set of inputs and gives an output stating whether a given search condition is satisfied or not. Equality, less-than, and greater-than comparisons are widely used as search conditions. In this paper, we show synthesis of quaternary equality, less-than, and greater-than comparators on the top of ion-trap realizable 1-qudit gates and 2-qudit Muthukrishnan–Stroud gates.